1. Technical Field
The present invention relates to a receiver for a firearm, the receiver being suitable for use in an AR15/M16 style rifle. In optional embodiments, the receiver may be used with various configurations and adaptations of AR15/M16 style rifles, including but not limited to direct impingement and piston-operated configurations. In yet further optional embodiments, the invention may include a firearm configured with the receiver disclosed herein or further may include a method of extending the operating life of a firearm.
2. Background of the Art
In the field of firearms, there are a multitude of different designs and types of rifles. One popular model includes what is known as the AR-15 rifle. Generally speaking, the AR-15 rifle was an abbreviation for the Armalite Model 15 rifle, which is understood to refer to a semi-automatic firearm having a design based on the original design of Eugene Stoner. While AR-15 is still a federally registered trademark of Colt, the populous uses the term AR-15 to refer to the general style of rifle which is available from a wide number of manufacturers, produced both in the United States and overseas. Other designations for similarly styled rifles are used, including both M4 and M16, referring to United States military variants, which may optionally include selective fire options. Additionally, the design is considered one of a modular nature and can include pistol variants as well.
Most AR-15/M16 style rifles use a mechanism of operation which can be understood to be a direct gas impingement system. With such system, high pressure gas acts directly upon the bolt and the carrier containing the bolt, eliminating the need for a piston or separate gas cylinder. Upon firing an AR-15/M16 style rifle, gas generated from the detonation of the powder moves through a gas port located in the top area of a barrel. Gas flows through the gas port into the gas block where it is directed into a gas tube, running generally about parallel with the barrel. The gas tube protrudes into the upper receiver of the AR-15/M16 style rifle and extends into the bolt carrier key (also referred to as a “gas key”) which directs gas into the bolt carrier. In turning down into the bolt carrier, the gas has space to expand within the carrier and forces the bolt carrier rearward toward the stock of the AR-15/M16 style rifle while forcing the bolt forward. This movement essentially unlocks the bolt from the forward position where the original detonation of the round took place. During the rearward movement of the carrier, a cam pin in the bolt necessitates that the bolt rotates and unlocks from the barrel extension of the barrel within the upper receiver. Thus, both the carrier and bolt move rearward together which extracts the empty cartridge prior to moving forward again, while a new round is chambered.
As previously mentioned, there exist further variants of AR-15/M16 style rifles that include piston operating systems. In such variants, a piston rod may be used that reciprocally moves between at least two positions. The piston can be coupled to the bolt carrier for movement of the bolt carrier from a first closed position to the open position, similarly to the movement obtained with a direct gas impingement operating system. In further optional embodiments, the piston is not attached to the bolt carrier but rather is simply in physical contact with the bolt carrier and thus can apply pressure to create movement. To function, gas generated from a detonated round flows through the gas port but instead of flowing down a gas tube as occurs with direct impingement operating systems, the gas forcefully acts on the face of the piston. This action drives the piston rearward and a rod or shaft in connection with the piston as well, which in turn applies abrupt force to the bolt carrier, having the rotatable bolt with cam pin. The bolt carrier moves rearward, the spent cartridge is ejected and the cycling commences similar to a direct impingement system, yet no gas directly acts upon the bolt and carrier.
Further considerations in the design of an operating system for an AR-15/M16 style rifle include considerations on the use of suppressors with the rifle, which may have an impact upon the amount of gas returning to the bolt and carrier in a direct impingement system or the speed of the piston and rod in a piston operating system. Such usage can accelerate wear on the firearm or alternative affect the performance.
In the AR-15/M16 style rifle, the upper receiver houses the bolt and carrier as well contains the opening for the extension of the barrel to within the interior of the receiver and a relief area that allows the cam pin to index out of the tract. Within the upper receiver of this style of rifle is also a track for the cam pin. In operating the firearm, the cam pin can create wear within the upper receiver, especially where the cam pin cams over into the tract relief area. Over time, this can result in wear into the receiver as most often the cam pin is of harden steel as it must withstand the force generated by detonating rounds.
In some instances, this cam pin-created wear can result in significant indentations and/or gouges in the upper receiver, possibly causing issues with the functionality of the rifle. While this issue can occur with direct impingement operating systems, the use of gas piston systems of various types can also cause this wear, resulting in deterioration of the upper receiver. Furthermore, as the use of suppressors has steadily become more common, the increased flow of gas may also exacerbate this issue, thus resulting in increased receiver wear. What is desired is a way of decreasing wear on the receiver of an AR-15/M16 style rifle.